1. Field of the Invention
The present invention relates to a passivation composition and a method of forming a conductive pattern by using the passivation composition. Specifically, the present invention relates to a passivation composition comprising an oxidizing agent and an inorganic base and a method of forming a conductive pattern by using the passivation composition.
2. Descriptions of the Related Art
Recently, with vigorous development of flat displays such as liquid crystal displays, plasma display panels, and touch screens, the development of the transparent electrode material for these devices has gained increasing attention. Generally, the material of transparent electrodes could be roughly divided into two categories, i.e., conductive metal oxides and conductive polymers. The examples of conductive metal oxides include indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), etc. Even these metal oxides have superior conductivities, but their applications are still limited due to their poor flexibility (i.e., poor elasticity and crisp character), high price (especially ITO) and high production costs. Especially, they are not suitable for flexible displays. The examples of conductive polymer include polythiophene, polyaniline, polyacetylene, polypyrrole, etc. The conductive polymer has gained increasing prominence due to their low-price and superior flexibilities.
Conventional methods for forming an electrode pattern of a display device using a conductive polymer may be roughly divided into etching and passivating methods. The etching method comprises the steps of forming a conductive polymer layer on a (transparent) substrate, covering a predetermined circuit area (i.e. a conductive area) with a mask, and then removing the conductive polymer at the non-circuit area (i.e. a non-conductive area) by using an etching agent to provide a patterned circuit. However, the product prepared by an etching method usually encounters problems such as height drop and dark lines resulting from different optical contrast because the conductive polymer only remains on a part of the substrate (only on the conductive area but not on the non-conductive area). In view of this, passivating methods are developed.
A conventional passivating method comprises passivating the conductive polymer material of non-circuit area to significantly reduce the conductivity of the non-circuit area to provide a desired patterned circuit by using an oxidizing agent. Although the conventional passivating method could solve the problems of height drop and optical contrast difference, it still has some deficiencies, such as insufficient passivating effect and poor durability of the product.
For example, TW 552591 discloses a method of manufacturing conductive pattern, which prints a solution with an oxidizing agent (as a passivating agent) onto the conductive polymer layer on the substrate to passivate the printed conductive polymer material to form a non-conductive area. However, the above described process has the following defects. First, the oxidizing agent is provided with flowability. The circuit area is not protected or isolated. The oxidizing agent may also etch the conductive material of the circuit area and as a result, distort the conductive pattern. The conductive pattern may be further etched during the subsequent washing and removal process of the oxidizing agent. Second, the viscosity of the oxidizing agent is usually increased to reduce its flowability to lower the influence of the oxidizing agent to the conductive pattern. However, this will inevitably slow down the spread of the oxidizing agent. There is, therefore, a contradiction between the passivating time and the passivating effect. In addition, in the conventional passivating method, the oxidizing agent only passivates the superficial part of a conductive polymer layer, the passivated part tends to be worn out to thereby expose the un-passivated part of the conductive polymer layer after a long-term use, and this will cause a short circuit. JP 2011-054617A discloses another one method of forming a conductive pattern, comprising providing a pattern film containing a passivating agent, and then forming conductive pattern by contacting the pattern film with a conductive polymer layer to passivate the contacted conductive polymer material. However, the method still can only passivate the superficial part of the conductive polymer layer. The problem of durability still exists, and moreover, the passivating effect is not sufficient because the level of the difference of the conductivities between the passivated area and the un-passivated area are merely about 105 to 106 times high.
The present invention provides a passivation composition for forming a conductive pattern and a method of using the passivation composition to form a conductive pattern. The passivating speed of the passivation composition of the present invention is fast. The passivating time therefore could be shortened, while the passivating effect provided by the passivation composition of the present invention is excellent because the variation of the conductivities before and after the passivating process reaches at least about 1012 times high. The passivation composition of the present invention could especially passivate the deep material of a conductive polymer layer and thereby, could improve the durability problem encountered due to the wear of the passivated material.